text: Chlorination of organic isothiocyanates is also well established: 
  :RN=C=S  +  2Cl  →  RN=CCl  +  SCl
  Alkylisocyanates are chlorinated by phosphorus pentachloride:
  :RN=C=O  +  PCl  →  RN=CCl  +  POCl
  Cyanogen chloride also chlorinates to give the isocyanide dichloride:
  :ClCN  +  Cl  →  ClN=CCl